1. Field of the Invention
The present invention relates to a vibrating gyroscope, and more particularly to a vibrating gyroscope used, for example, to detect angular velocities for prevention of camera shake.
2. Description of the Related Art
FIG. 11 is a perspective view of an example of a conventional vibrating gyroscope. A vibrating gyroscope 1 includes a vibrating body 2 in, for example, the shape of a regular triangle. As seen in FIGS. 11 and 12, three peripheral surfaces of the vibrating body 2 have piezoelectric elements 3a, 3b, and 3c, respectively. To use the vibrating gyroscope 1, as shown in FIG. 12, for example, a vibration circuit 4 is connected between the piezoelectric elements 3a and 3b and the piezoelectric element 3c. Also, the piezoelectric elements 3a and 3b are connected to a detection circuit 5. The detection circuit 5 includes, for example, a differential circuit, a synchronous detection circuit, a smoothing circuit, and a DC amplifying circuit.
In the vibrating gyroscope 1, a signal outputted from the piezoelectric element 3c is returned to the vibration circuit 4. The vibration circuit 4 amplifies the returned signal and compensates the amplified signal in phase, thereby forming an exciting signal. The exciting signal thus obtained is fed to the piezoelectric elements 3a and 3b. This causes the vibrating body 2 to perform bending vibrations in the direction perpendicular to the surface where the piezoelectric element 3c is formed. In this state, bending states of the piezoelectric elements 3a and 3b are the same, and signals outputted therefrom are also the same. Therefore, no signal is outputted from the differential circuit in the detection circuit 5. In a state where the vibrating body 2 is in bending vibration, rotation about an axis of the vibrating body 2 in the center generates a Coriolis force, thereby changing the vibration direction of the vibrating body 2. This causes a difference between signals outputted from the piezoelectric elements 3a and 3b, and causes the differential circuit to output a signal. The output signal is then smoothed in the smoothing circuit, and the smoothed signal is amplified in the DC amplifying circuit. Therefore, measuring a signal outputted from the detection circuit 5 allows an angular rotation velocity to be detected.
For a vibrating gyroscope 1 shown in FIG. 13, a vibrating body 2 may be manufactured by coupling two piezoelectric substrates 6a and 6b. As indicated by arrows in FIG. 13, the piezoelectric substrates are polarized so as to oppose each other. In this case, electrodes 7a and 7b each extending in the length direction are formed on one of opposing surfaces of the vibrating body 2, and an electrode 8 is formed on the entire surface of the other opposing surfaces thereof. Using the circuits shown in FIG. 12, the described vibrating gyroscope 1 also allows the angular velocity to be detected.
Nevertheless, with each of the vibrating gyroscopes described above, only the angular velocity about the axis of the vibrating body in the center can be detected, and only the angular velocity with respect to a single direction can be detected. Therefore, two units of the vibrating gyroscopes are required to detect angular velocities in two directions, and two vibration circuits are required to excite these vibrating gyroscopes. The vibration circuit is expensive, thereby increasing costs to detect angular velocities in multiple directions.
In view of the forgoing reasons, there has been a demand for a vibrating gyroscope capable of detecting angular velocities with respect to two directions by using a single element.